Freed from the chilling ice, the elemental took a step further in order to protect its host. Its water began to spread all over the Admiral then swallowed him whole, putting him inside the protection of its liquid body.
Mer can hold their breath for a significant amount of time, so being there doesn't posses any threat to his life. Quite the opposite, he's now safe from any danger from the outside, as long as the elemental remains alive.
And from Dov's observation, seems like an element reaction like freezing, can only affect the outer layer of the creature, so even if Celene struck the thing with lightning, the Admiral won't be affected by it.
"*Sigh* why does every level 75 personal passive so damn annoying?"
A little rant from Dov, seeing how thick the layer was from the elemental skin to the Admiral. He can't see any way for them to defeat that Master ranked adventurer until they get rid of the [Avatar of the Sea King].